1. Field of the Invention
This invention relates to apparatus for removing bulk material from a dump, comprising a horizontal scooping tube, which is mounted for rotation about its axis and provided with a plurality of buckets, which are distributed around the periphery and over the length of the scooping tube and protrude into the interior of the scooping tube through entrance openings formed in the wall of the scooping tube, and a conveyor, which extends within the scooping tube and serves to receive bulk material which has been dropped through the entrance openings by the buckets.
2. Description of the Prior Art
Scooping tubes of that kind have been disclosed in German Patent Publication No. 1,229,912 and compared with other apparatus for removing bulk material afford the advantage that material can be removed from a dump of bulk material throughout the width of the dump at the same time and the bulk material discharged from the scooping tube will be throughly mixed. In order to ensure that the bulk material which has been removed from the dump can be reliably delivered to the conveyor within the scooping tube, the side walls of the buckets and their rear wall, which connects said side walls, protrude into the interior of the scooping tube and the discharge edge of each bucket is in pressure contact with a guide wall so that any bulk material which falls prematurely from the buckets into the interior of the scooping tube will be pushed by the back of the bucket along the guide wall to the conveyor. Those portions of the bucket which protrude into the interior of the scooping tube consist of elastic material so that a sealing engagement between said portions and the guide wall can be ensured and the separation of the bulk material from the bucket walls will be assisted by wall movements. A main disadvantage of such apparatus for removing bulk material resides in that the scooping forces which can be transmitted from the buckets to the scooping tube to which said buckets are connected by screws are restricted because excessively high loads would otherwise be applied in local regions.
In order to permit a taking up of relatively large scooping forces, stiffening means are provided within the scooping tube. But such scooping tube will promote an accumulation of bulk material which has been removed and which when dropped from the entrance openings is not received by the conveyor but elsewhere in the interior of the scooping tube. In order to avoid that disadvantage a scooping tube has been disclosed in Austrian Patent Specification No. 291,852 which comprises an outer shell and an inner shell, which is coaxially arranged in and spaced from the outer shell. Because the required stiffeners can be disposed between the two shells of the scooping tube and the entrance openings are constituted by ducts, which connect the two shells, the bulk material which has been removed can drop only into the interior of the inner shell, which surrounds a space that is enclosed by a smooth surface and does not permit an accumulation of material. A disadvantage of those known scooping tubes resides in that the provision of two shells substantially increases the structural expenditure and the buckets cannot be mounted at any desired locations because stiffening means are provided between the two shells and ducts must be provided between the two shells. Besides, the ducts joining the buckets are subjected to a relatively large wear.